/*
 * $HeadURL: http://svn.apache.org/repos/asf/httpcomponents/httpcore/trunk/module-main/src/main/java/org/apache/http/message/HeaderValueFormatter.java $
 * $Revision: 571954 $
 * $Date: 2007-09-02 04:05:21 -0700 (Sun, 02 Sep 2007) $
 *
 * ====================================================================
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 *
 */

package org.apache.http.message;

import org.apache.http.HeaderElement;
import org.apache.http.NameValuePair;
import org.apache.http.util.CharArrayBuffer;

/**
 * Interface for formatting elements of a header value. This is the complement
 * to {@link HeaderValueParser}. Instances of this interface are expected to be
 * stateless and thread-safe.
 * 
 * <p>
 * All formatting methods accept an optional buffer argument. If a buffer is
 * passed in, the formatted element will be appended and the modified buffer is
 * returned. If no buffer is passed in, a new buffer will be created and filled
 * with the formatted element. In both cases, the caller is allowed to modify
 * the returned buffer.
 * </p>
 * 
 * 
 * <!-- empty lines above to avoid 'svn diff' context problems -->
 * 
 * @version $Revision: 571954 $
 * 
 * @since 4.0
 */
public interface HeaderValueFormatter {

    /**
     * Formats an array of header elements.
     * 
     * @param buffer
     *            the buffer to append to, or <code>null</code> to create a new
     *            buffer
     * @param elems
     *            the header elements to format
     * @param quote
     *            <code>true</code> to always format with quoted values,
     *            <code>false</code> to use quotes only when necessary
     * 
     * @return a buffer with the formatted header elements. If the
     *         <code>buffer</code> argument was not <code>null</code>, that
     *         buffer will be used and returned.
     */
    CharArrayBuffer formatElements(CharArrayBuffer buffer,
            HeaderElement[] elems, boolean quote);

    /**
     * Formats one header element.
     * 
     * @param buffer
     *            the buffer to append to, or <code>null</code> to create a new
     *            buffer
     * @param elem
     *            the header element to format
     * @param quote
     *            <code>true</code> to always format with quoted values,
     *            <code>false</code> to use quotes only when necessary
     * 
     * @return a buffer with the formatted header element. If the
     *         <code>buffer</code> argument was not <code>null</code>, that
     *         buffer will be used and returned.
     */
    CharArrayBuffer formatHeaderElement(CharArrayBuffer buffer,
            HeaderElement elem, boolean quote);

    /**
     * Formats the parameters of a header element. That's a list of name-value
     * pairs, to be separated by semicolons. This method will <i>not</i>
     * generate a leading semicolon.
     * 
     * @param buffer
     *            the buffer to append to, or <code>null</code> to create a new
     *            buffer
     * @param nvps
     *            the parameters (name-value pairs) to format
     * @param quote
     *            <code>true</code> to always format with quoted values,
     *            <code>false</code> to use quotes only when necessary
     * 
     * @return a buffer with the formatted parameters. If the
     *         <code>buffer</code> argument was not <code>null</code>, that
     *         buffer will be used and returned.
     */
    CharArrayBuffer formatParameters(CharArrayBuffer buffer,
            NameValuePair[] nvps, boolean quote);

    /**
     * Formats one name-value pair, where the value is optional.
     * 
     * @param buffer
     *            the buffer to append to, or <code>null</code> to create a new
     *            buffer
     * @param nvp
     *            the name-value pair to format
     * @param quote
     *            <code>true</code> to always format with a quoted value,
     *            <code>false</code> to use quotes only when necessary
     * 
     * @return a buffer with the formatted name-value pair. If the
     *         <code>buffer</code> argument was not <code>null</code>, that
     *         buffer will be used and returned.
     */
    CharArrayBuffer formatNameValuePair(CharArrayBuffer buffer,
            NameValuePair nvp, boolean quote);

}
